Among the known printers are printers that carry out printing on a print medium in the form of a long sheet unwound from a feed roller and have a take-up roller collect the printing-completed medium. The printers of this type are equipped with a transport mechanism. The transport mechanism transports the print medium held on the upstream side, in the transport direction of the print medium, relative to a printing unit in charge of carrying out printing on the print medium. Such printers may further have a tension applying mechanism between the feed roller or the take-up roller and the printing unit. The tension applying member applies a predetermined tension to the print medium so as to unwind or take up the print medium without creasing or slackening it. The tension to be applied then may differ depending on a print medium selected and used, a printing speed, and contents to be printed on the medium. To deal with this, a tension applying mechanism was proposed. The tension applying mechanism includes a tension bar 1001 structured as illustrated in FIG. 10, and a counterweight 1002 on a side facing an oscillatory rotation shaft 1003. This mechanism is operable to change a tension to be applied by adjusting the weight of the counterweight 1002.
The tension applying mechanism thus structured needs a space for movement of the counterweight 1002 and an arm 1004 supporting the tension bar, in addition to a space for movements of the tension bar. This may be a bottleneck in the pursuit of space saving. In the meantime, a linear tension applying mechanisms requiring no oscillatory rotation shaft was proposed, as described in Japanese Patent No. 5334986. To keep the tension bar horizontally, the tension applying mechanism structured as described in Japanese Patent No. 5334986 has pinions at both ends of the tension bar and a rack on one side of the tension bar closer to a support unit. The pinions and the rack are engaged with each other so as to keep a balance between the two ends. This known tension applying mechanism, in order to apply a bias to a print medium, uses the self weight of the tension bar and weights hanging with ropes from the ends of the tension bar.